Among color image display devices for computers and television sets, plasma display panels (hereinafter referred to as PDPs) have become a focus of much expectation due to its ability to realize thin display panels. Especially, because a PDP is viewable at wide angles and has excellent characteristics such as rapid response, many companies and research institutes have aggressively pursued development of PDPs toward the popularization of the same.
In such a PDP, a plurality of electrodes are disposed on a front glass substrate and a back glass substrate; the two substrates face each other with a spacing member sandwiched therebetween in such a manner that the electrodes on either substrate are at right angles to the electrodes on the other substrate, and discharge gas is enclosed in the space between the two substrates. A dielectric layer covering the electrodes coats a surface of the front glass substrate that faces the back glass substrate, and further, a protective layer made of MgO coats the dielectric layer.
When driving PDPs, electrical charges are formed on the surface of the protective layer at cells to emit light by performing address discharge between the electrodes on the front and the back glass substrates, and sustained discharge is carried out between electrodes adjacent to the cell, on which the electric charge is formed, on the front glass substrate. The protective layer on which the electric charge is formed is for protecting both the dielectric layer and the electrodes from ion bombardment (sputtering) generated when address discharge and sustained discharge are carried out. The protective layer also has memory function for emitting secondary electron and holding electric charges while address discharge. Therefore, magnesium oxide (MgO) is commonly used for a protective layer because MgO is excellent in both anti-sputtering and secondary electron emission properties.
In recent years, demand for the expansion of life of PDPs has been growing. Japanese Laid-Open Patent Application No. H10-106441 teaches a technique, in which a protective layer is evaporated in an atmosphere containing water vapor, as one solution to meet such a demand. According to H10-106441, the protective layer with (110) plane orientation in a thickness direction of the layer is formed. Because (110) plane orientation results in high anti-sputtering property, erosion of the protective layer is suppressed and it becomes possible to prolong the life of PDPs.